聚苯乙烯非晶区结构的RDF研究

本文介绍了以X-射线衍射法测定非品区结构的径向分市函数RDF方法，并将其应用于聚苯乙烯（PS）非晶区的结构研究．     

高斯多峰拟合在径向分布函数中的应用

利用同步辐射X射线散射法测定了盐水摩尔比分别为1:30和1:14的Rb2SO4和Cs2SO4的水溶液结构. 通过对散射数据的处理, 获得了两种溶液的径向分布函数. 采用多峰拟合中的Gaussian法对径向分布函数中金属离子第一水合层附近的叠加峰进行了处理, 多峰拟合结果与实验结果吻合得很好. 通过将拟合数据与已报道的溶液结构和晶体结构对比分析, 确定了每个拟合峰的归属.多峰拟合结果分析表明, Rb+和Cs+第一水合层配位数为6, 为变形的八面体构型. 两种溶液中都存在着金属离子和硫酸根离子接触离子对: Rb—S 和Cs—S 的特征距离分别为0.407和0.427 nm. 研究证实, 多峰拟合有助于阐述溶液中离子的水合结构.     

A New Perturbed Hard-Sphere Equation of State

In 1873 van der Waals1 proposed a two-parameter cubic equation of state (EOS), which provides a rather clear physical picture of molecular interactions in real fluids. Because of its simplicity, it soon was widely used. Other famous equations of state, such as PR2, Soave3, have been proposed since then. But all these equations are not accurate enough when applied to liquid phase.The trend of modeling the properties of fluids is that a single equation of state can be applied to both vapor an…     

Local Structure Analysis and Modelling of Lignin-Based Carbon Composites through the Hierarchical Decomposition of the Radial Distribution Function

Carbonized lignin has been proposed as a sustainable and domestic source of activated, amorphous, graphitic, and nanostructured carbon for many industrial applications as the structure can be tuned through processing conditions. However, the inherent variability of lignin and its complex physicochemical structure resulting from feedstock and pulping selection make the Process-Structure-Property-Performance (PSPP) relationships hard to define. In this work, radial distribution functions (RDFs) from synchrotron X-ray and neutron scattering of lignin-based carbon composites (LBCCs) are investigated using the Hierarchical Decomposition of the Radial Distribution Function (HDRDF) modelling method to characterize the local atomic environment and develop quantitative PSPP relationships. PSPP relationships for LBCCs defined by this work include crystallite size dependence on lignin feedstock as well as increasing crystalline volume fraction, nanoscale composite density, and crystallite size with increasing reduction temperature.     

Tentative Comparison of Tube Radial Distribution Chromatography and CZE

Tube radical distribution chromatography (TRDC) uses an untreated open tubular capillary tube and a ternary mixture of solvents (water and hydrophilic/hydrophobic organic solvents) as a carrier solution. A model analyte mixture comprising 1-naphthol, 1-naphthoic acid, 1-naphthalenesulfonic acid, 2,6-naphthalenedisulfonic acid, and 1,3,6-naphthalenetrisulfonic acid was examined by the TRDC and capillary zone electrophoresis (CZE) systems that comprised mainly a capillary tube and a detector. In the TRDC system the elution order of analytes could be changed by altering the component ratios of the solvents, whereas in the CZE system the elution order was changed by altering the electroosmotic flow direction. The experimental data obtained provide clues about the features and utility of TRDC as a new separation method.     

径向基函数神经网络用于重叠色谱峰解析

 在高斯基径向基函数神经网络 (RBFNN)学习算法中引入了鲁棒性和随机全局寻优的两阶段遗传算法 :结构学习和参数优化。通过两阶段学习算法的交替使用 ,使网络具有结构自学习和参数优化的能力 ,而后将网络应用于组分数未知的重叠色谱峰解析。该方法具有不需人为干预 ,可自动确定网络结构即组分数的优点 ;并且解析精度较高 ,适用于多组分重叠色谱峰的解析 ;对完全重叠色谱峰也具有良好的解析能力。     

从麦克斯韦速度分布函数直接推导高分子链末端距分布函数

利用高分子链末端距分布与小分子运动速度分布之间的相关性 ,从熟知的麦克斯韦速度分布函数直接推导出高分子链末端距的径向分布函数 ,并从量变到质变的观点对高分子和小分子运动的统计规律进行讨论     

Radial Basis Function Networks Applied in Bacterial Classification Based on MALDI-TOF-MS

IntroductionWith the improvement of living standard,people pay more and more attention to health.Theaccurate and sensitive identification ofmicroorganisms plays an important role indiagnosing disease,identifying public healthhazards from pathogens,monitoring potential foodcontamination,regulating bioprocessingoperations,and detecting or identifying the natureof biological agents[1,2 ] . There are two major goalsfor the identification of microorganisms. Onewould be to develop a method to use in…     

Distribution Function and Thermodynamic Potentials of a Self‐Avoiding Chain

Summary: An explicit expression is derived for the distribution function of end‐to‐end vectors for a flexible self‐avoiding chain. Based on this relation, analytical formulas are developed for the free and internal energies of a chain with excluded‐volume interactions. Force–stretch relations are obtained at uniaxial tension and compression. The effects of strength of segment interactions on the shapes of the distribution function and the force‐displacement diagram, as well as on the mean‐square end‐to‐end distance and stiffness of a chain are studied numerically.

The dimensionless distribution function P versus the dimensionless end‐to‐end vector Q^* for self‐repellent chains with χ = 0.0, 0.4, 0.8, 1.2, and 1.6, from top to bottom, respectively.     

密闭式电喷雾离子源中流场的分布特征

利用流体力学模拟软件Fluent构建了电喷雾离子源的二维模型,并基于所构建的模型探讨了离子源构型、辅助气引入方式、气体流速对源内流场分布的影响。结果表明,相比于其它两种结构,矩形结构的离子源能够提供较为稳定的流场。通入同轴辅助气和正交方向辅助气都能够起到聚集样品喷雾的效果,但作用效果却并不相同。提高同轴辅助气流速,能够增大喷口处混返区域,改变气流驻点位置。而增大正交方向辅助气流速,虽然同样能够提高源内各处气体流速,但并不会改变喷口处混返区域的大小。以Turbo V离子源为研究对象,考察了喷针位置、辅助气流速对溶液总离子流的影响,实验趋势与模拟结果基本吻合。     

非自由态Cu(Ⅱ)的径向波函数及其电子结构

本文利用非自由态离子的标度径向理论给出了非自由态Cu(Ⅱ)的3d径向波函数,讨论了Jahn-Teller效应对非自由度的影响。计算了一些Cu(Ⅱ)络合物的d-d电子光谱和g-因子,计算结果与实验值较为一致。     

Rapid Determination of Methotrexate and 7-Hydroxymethotrexate in Serum and Cerebrospinal Fluid by Radial Compression Liquid Chromatography

Abstract

A rapid, specific and sensitive radial compression reverse phase liquid chromatographic method for the analysis of methotrexate and 7-hydroxymethotrexate in serum and cerebrospinal fluid is reported. A mobile phase consisting of acetonitrile-methanol-pH 3 phosphate (8:15:77) at 6 ml/min flow rate was employed. The U.V. detector was set at 317 nm, and folic acid was used as an internal standard. A rapid extraction of methotrexate and 7-hydroxymethotrexate was performed using Sep-Pak cartridges with high extraction efficiency for both compounds. Patients serum and cerebrospinal fluid samples were analyzed by the described method and the concentrations of methotrexate were compared to those obtained by an enzyme immunoassay. No interference from other metabolites or anticancer drugs in the described assay was observed.     

非自由态Mn(Ⅱ)的径向波函数及其电子结构

应用非自由态离子标度径向理论,以“非自由度”作为衡量非自由态的指标,从实验值求出过渡系数,得到了非自由Mn(Ⅱ)的径向波函数。利用该函数计算了一些Mn(Ⅱ)络合物的d-d电子光谱,计算结果与实验值较为一致。     

园柱分布函数计算程序及其应用

对表征轴向拉伸非晶聚合物结构的圆柱分布函数（ＣＤＦ）计算方法进行了讨论，介绍了作者编写的园柱分布函数ＣＤＦ９２型程序计算的可靠性，并由聚对苯二甲酸乙二醇酯（ＰＥＴ）轴取向非晶薄膜的二维相干散射强度计算其ＣＤＦ，据此对所获得的精细结构信息进行了分析。研究表明，该ＣＤＦ９２型程序计算结果可靠，在高聚物结构研究中具有广泛的实用性。     

Detection of Cholangiocarcinoma with Fourier Transform Infrared Spectroscopy and Radial Basis Function Neural Network Classification

The aim of this study was to explore the possibility of applying Fourier transform infrared(FTIR) spectroscopy as a medical diagnostic tool based on a neural network classifier for detecting and classifying cholangiocarcinoma. A total of 51 cases of bile duct tissues were obtained and later characterized by FTIR spectroscopy prior to pathological diagnosis. The criteria for classification included 30 parameters for each FTIR spectra, including peak position(P), intensity(I) and full width at half-maximum(FWHM), were measured, calculated and subsequently compared against the normal and cancer groups. The FTIR spectra were classified by the radial basis function(RBF) network model. For establishing the RBF, 23 cases were used to train the RBF classifier, and 28 cases were applied to validate the model. Using the RFB model, nine parameters were observed to be pronouncedly different between cancerous and normal tissue, including I₁₆₄₀, I₁₅₅₀, I₁₄₆₀, I₁₄₀₀, I₁₂₅₀, I₁₁₂₀, I₁₀₈₀, I₁₀₄₀ and P₁₀₄₀. In the RBF training classification, the accuracy, sensitivity, and specificity of diagnosis were 82.6%, 80.0%, and 84.6%, respectively. While validating the classification, the accuracy, sensitivity, and specificity of diagnosis were 78.6%, 75.0%, and 81.2%, respectively. The results suggest that FTIR spectroscopy combined with neural network classifier could be applied as a medical diagnostic tool in cholangiocarcinoma diagnosis.     

磷酸二氢铵水溶液构型能删和径向分布函数的分子动力学模拟

采用分子动力学模拟对不同温度下磷酸二氢铵水溶液的构型能和径向分布函数进行了研究．磷酸二氢根被看作七节点模型,铵离子被看作五节点模型,而水分子则被看作简单点电荷模型．在饱和温度附近,体系局域粒子数密度有波动．373-400K的溶液势能增长缓慢表明磷酸二氧铵部分分解．磷酸二氢根中的氧原子与铵离子中氢原子的径向分布函数在三种不同温度下呈现明显不同,表明溶液中平均氢键数目随温度的变化明显改变．温度对磷酸二氢根中的氧原子和氧原子的结合有一定的影响,而在饱和溶液中有更多的生长基无产生．     

N-Alkanes in an Equatorial Sedimentary Environment: Their Distribution as a Function of Particle Size

Abstract

In order to investigate the biogeochemistry of organic matter deposited in an equatorial deltaic environment, the Mahakam delta, Borneo, analysis of geochemical markers has been realised both on various sediments and on sediments separated as a function of particle size.

Sediments were selected from two levels (-150m and -500m) of a continuous core sampled in the Mahakam delta in 1981 (Misedor Programme) and represent various lithotypes of the deltaic environment and different diagenetic conditions. After separation into sand size (> 50 μm), silt size (50–5 4mUm) and clay size (< 5 μm) fractions, free lipids have been extracted and hydrocarbons isolated by micro-column chromatography, and analysed by capillary gas liquid chromatography. Concentrations and carbon number distributions of n-alkanes are discussed in terms of the relationship between the sedimentary environment and the importance of terrigenous inputs. The distribution patterns of n-alkanes of different sediment size fractions are characterized by the predominance of high molecular weight compounds in the range C23–C37, which are also encountered for the actual deltaic plain flora: mangrove and nipah-nipah. Carbon Preference Index (CPI) values are higher in the coarse and intermediate fractions reflecting their enrichment in continentally-derived vegetation debris.     

毛细管电泳径向基神经网络校正法定量分析核苷

采用径向基神经网络算法对一组已知样品的核苷及内标物浓度与毛细管电泳峰面积数据进行回归计算,建立峰面积与核苷浓度之间的关系模型,对未知样品中待测核苷浓度作出预测,形成了毛细管电泳定量分析新方法．将其用于鸟嘌呤核苷含量测定,所建模型预测结果平均相对误差为0．86％,明显低于线性回归及BP神经网络模型的2．60％和1．07％．研究结果表明,本方法简便易用,能有效提高毛细管电泳定量分析的准确度,优于线性回归及BP神经网络法．